Filter system



All@ 15, 1950 o. M. sUMMERs 2,518,835

' FILTER SYSTEM 2" ATTORNEYS o. M. suMMERs FILTER SYSTEM Aug. l5, 1950 Filed Feb. 13, 1946 5 Sheets-Sheet 2 OTTO M.SUMMERS ALVM@ HTTDENEEE Aug. 15, 195o O. M. SUMMERS Aug? 15, 1950 o. M. suMMERs 2,518,835

u FILTER SYSTEM Filed Feb. 13, 1946 25 5| 5 2%( g YQ S 55 56 57 x 54 1 NVENTQR OTTO MSUMMERS HTTD RNEES Aug. 15, A1950 o. M. suMMl-:Rs 2,518,835

FILTER SYSTEM Filed Feb. 15, 194e 5 sheets-sheet 5 Fimov INZE NTE OTTO M.SUMMERS E? f YMZM Patented Aug. l', Q

FILTER SYSTEM Otto Murray Summers, Glasgow, Ky., assignor to The Thompson Grinder Company, Springfield, Ohio, a corporation of Ohio Application' February 13, 1946, Serial No. 647,245

` s claims. (o1. 21o-150) The present invention relates to structure for filtering lubricating fluids, particularly those which are used in connection with the various machines such as grinderslathes, etc.

In the case of grinding-machines, it is customary to use a combined coolant and lubricating iiuid at the work surface of the grinding wheel in order to facilitate the abrasive action, to eliminate sparks, etc. This iluid is pumpedagainst the grinding wheel so as to iiow onto the work surface and the fluid then linds its Way, usually by gravitation, to a reservoir from which the fluid is again re-circulated, The line abrasive powder which is obtainedin part from the grinding wheel and also, in part from the work piece is carried by the coolant to the reservoir where it is permitted to settle out of solution and the pump draws from a region in which the liquid is l fairly clear. It is obvious that an arrangement of this character may work satisfactorily in case the metal particles or pieces areof such size as to Vdrop quickly by gravity into the settling tank so as effectively to remove themselves from the circulating fluid. However, in certain types of grinders, particularly those of high precision, extremely line cuts are made on the work piece and the metal particles may. be of microscopic size so that they go into suspension in the,r coolant fluid. The settling method of separating the solid material from the liquid would not be altogether satisfactory in cases of this kind because the Huid, when being returned by the pump to the grinding position, would contain certain amounts of metal particles which may greatly machine as a mass so as to be removed from A-the circulating iiuld. i Still another object is to provide filtering apparatus adapted for use in abrasive machines and in which no settling reservoir is necessary, but the filtering action is Iperformed yby elements contained in the fluid system. ,Y i

Another object is to provide an improved apparatus for finely separating solid particles of microscopic or other size from the fluid in which they are contained, said apparatus also serving to present the fluid from which the particles had been removed to a working surface.

A still further object is to provide apparatus of the character described in which the filtering or separating function can be carried to any degree of fineness by adding filtering or separation devices in order that the extreme degree of purity of the coolant is obtained so as to improve the cutting or abrasive action of the working tool on the work piece.

The above objects are attained in brief by employing structure consisting of one or more specially designed ltering units, connected in series and preferably of different coarseness, together with aprcvision for applying the force of gravity in the separation of the solid particles from the fluid which are then expelled from the reservoir.

Other features and objects will be apparent as the specication is perused in connection with the accompanying drawings in which:

Figure 1 represents a perspective View in a somewhat diagrammatic form of a grinder which is provided with the improved filtering or particle separating unit.

Figure 2 is a sectional view taken along line 2--2 in Figure 1 and showing in elevation the centrifugal pumps and their actuating motor for circulating the particle containing fluid through the filter structure.

Figure 3 is a longitudinal sectional view of the filtering unit and tank taken along line 3-3 in Figure 1.

Figure 4 is a sectional view somewhat enlarged, taken along line 4 4 in Figure 3 across one of the filtering elements.

Figure 5 is a longitudinal sectional view of the sludge or swarf pump for removing any settlings from the filter units.

Figure 6 is a fragmentary sectional end View of the pump shown in Figure 5, but in which the pistons are illustrated as having been moved to their retracted respective positions.

Figure 7 is a plan view of the star valve taken along line 1--1 in Figure 6 and in which the valve is positioned in line with the respective pistons of the pump.

Figure 8 is an enlarged sectional view taken along line 3 8 in Figure 3 and showing the seoond iilter element of the system.

Figure 9 represents a mid-section View of the filter unit shown in Figure 8, but of somewhat smaller size and in which the filter unit has been collapsed preparatory to receiving a charge of the particle-containing coolant.

Figure l() is a plan View looking down on top of the filter compartments, but with the top of each compartment removed so as to expose the entire elements.

Figure l1 is an enlarged fragmentary view of the device in sections for holding the filter bags in place.

Figure 12 is a view, greatly enlarged, of a smallpiece of the fabric used for the filters and indiH eating the manner in which the filtering or sediment-separating function takes place.

Referring more particularly to Figures 1 and 2, reference character i designates generally a grinding machine which is formed of a large base 2 containing the actuating apparatus, motors, gears, etc., for reciprocating a table 3 longitudie nally of the base. A guard i is provided at the end of the reciprocatory table and if desired, a stationary platform of ledge 5 may also be se` cured to the base for supporting Work pieces. The base 2 is provided at one end with a rearwardly and upwardly extending frame 3 to which a pair of vertical supports 'l maybe secured. The top of the frame 3 carries a large inverted shield 8 which extends over a horizontally disposed grinding wheel 3 suitably journalled as indicated at iii' from a sub-frame ii. The latter is supported in any suitable manner on a member l2 carried by the uprights l'. The base 2 also serves as a support for a vertically extending plate I3 which is positioned at the rear end of the travelling table or carriage 3 which serves as a guard against sparks moving toward the rear of the machine. A motor iii which is carried by the member l2 serves to rotate the grinding wheel 9 at a fast rate of speed. It will be understood that suitable mechanism is provided, manually or automatically controlled, for moving the grinding wheel s in a transverse direction so that a work piece placed on the travelling table 3 can be groLmd to any desired size or shape.

It has been customary to apply a coolant to the grinding wheel 9, this fluid serving to reduce the temperature at the abradcd surface as Well as to reduce the sparking effects. The coolant is usually supplied, through a pipe or conduit i5 to a suitably shaped nozzle E6 positioned at a convenient place near the grinding wheel. The coolant, after being emitted at the nozzle, flows by gravity onto the table 3, then through an elongated trough l'l extending along the rear edge of the table (Figure 2) into a U-shaped 'compartment i8 formed in the base 2. From this compartment the coolant is usually run into a reservoir (not shown) and there allowed to remain throughout a settling period `during which the metal particles tend to separate out of solution and thus drop into the bottom of the reservoir. A pump takes the coolant from which the particles have separated and forces the coolant through a exible pipe I@ to a stationary conduit 26 which is connected to the conduit i5. A structure of this general character has been more or less satisfactory in cases where the grinding is of a rough type so that the particles are quite coarse or large, and therefore tend to settle in the reservoir rather quickly, However, in the case of precision grinding in which only extremely small cuts are taken at any one time and the particles are therefore microscopically small, 'it is found that such particles go into solution with the coolant and remain for the moet part suspended in the liquid. In the case of prior art machines, the fluid pump would, therefore, force this particle-containing fluid into the nozzle I6 and these particles would generally interfere with the griding operation, either by Way of making the depth of out inaccurate or bumpy or else by spoiling the character of the surface.

In accordance with one of the aspects of my invention, an improved filter structure and system has been provided by which practically all of the' particles, regardless of size, microscopic or larger, are completely removed from the coolant.

The improved filter' is conveniently housed in a: chamber 2 1; preferably of rectangular shape and may be formed of heavy sheet metal or cast as a member integral with the body 2. The sides of the chamber or compartment 2| are indicated at 22, 23' (Figure 3) and 24 (Figure l). The top and bottom closures of the box are indicatedV at25`- and 26 respectively. There is a pair of spaced partitions 271, 28 extending transversely across the box preferably made of heavy sheet metal-so as to'di'vide the box or compartment into three sections indicated generally at 2S, 3e and 3i respectively (Figure 3).

The first section 2`9 includes a pair of vertically mounted superposed centrifugal pumps 32, 33 and electric motor 34 for driving the pumps. For supporting these elements within the comu partrnent, a pair of transversely extending webs 35, 33 is employed. These webs have an opening for receiving a conicall'y shaped housing 3l which carries the pumps 32, 33. The housing may be supported from plates 38, bolted or othern wise secured to the webs 35, 3B. The motor is also contained within a housing 39 and the latter is supported in any suitable manner from the upper'plate' 38. A shaft 40 is suitably journalled within the housing 37 and also at the plates 33,

this shaft carrying at an intermediate and at an end position an impeller contained within the pump 'casings 3-2', 33. The upper end of the shaft is-A'suitably vconnected to the armature or rotor of the motor 34 so that'when the latter is actuated", the impellers in the pumps 32 and 33 are rotated ata relatively high speed. The structural arrangement is such that all rotating parts of the pumps 32, 33 yand of the motor 34 are rendered il'uidt'ight from the surrounding body of lubricating coolant. The outlet of the pump 32' mayr comprise a pair of pipe lengths` 4l connected together through a coupling 42 and supported in any Suitable manner from the upper vplate 38. The inlet of the pump 32 constitutes compartment 3l (Figure 3). The outlet conduit lli of vthe upper p ump 32 communicates with the flexible hose 1:9 Whichleads to the nozzle i5 (Figure rl).

The coolant which enters the inlet opening of the pump 32 is 'contained in the immediately surrounding space incoinpartment 29 and this compartment is'kept full by admitting iiuid through an opening 41 in the partition 27. This opening tcommunicatesr with the exterior surface of a l'--large filter unit generally indicated at 48 conamasser tained in the middle compartment so. The' inlet;

opening of the pump 33 obtains its coolant `from the liquid body immediately surrounding the pump in the lowermost compartment 29 and this compartment is maintained full by admitting coolant througha pipe 49 which leads from the rectangularly shaped groove I8 (Figure 2) vextending lengthwise of the base 2 at the rear edge thereof. Filter structure The filter through which the coolant passesto the inlet of the pump 32 is constituted of a pair of bags 50, 4spaced apart as shown in Figure 8 and arranged in an inverted position, i. e. the closed ends of the bags are at the bottom of the compartment 55. These bags have cylindrical portions 52, 53 respectively and lower spherical portions 54, 55. The portion 55 of the inner bag 5| may be inwardly joined to the cylindrical portion but the portion 54 of the outer bag is made separate from its cylindrical portion 52 and is attached thereto at the lower edge by means of a heavy metal ring 55 passing around the inner surface of a flanged extension of the portion 54.

A series of wire loops or strands 5'! serve to hold both thicknesses of the outer bag against the ring 56 as shownin Figure 8. The inner bag 5| is made of light material having a fairly tight weave and serves to filter and remove the scum from the coolant fluid. This inner bag is designed to be replaced daily since practically all of the foreign materialin the coolant which reaches this particular filter is caught by this inner lter element. The outer bag 55 is preferably made of fiberglass, canvas or other suitable material, for mechanical strength and for filtering the few particles which have passed through the inner scum bag.

There is provided for holding the bags in a suspended position and properly spaced, a ring 56 having a relatively wide ange 51 which rests on an inwardly extending web 53 secured to the walls of the compartment 30. The ring 56 is provided with a large number of peripherally positioned openings 59 preferably formed by an upsetting operation as indicated at 6D. These openings serve as an egress for fluid which may have collected at the top of the bags 50, 5| in case passage through one or both bags is partially stopped. The member 56 is provided at the bottom edge with a narrow ring of metal 6| of substantial thickness and formed by doubling a circular strip of material on itself and secured in any suitable manner to the element 56. The width of the annular ring 6i corresponds to the thickness of the space between the two bags 50, 5 I. A clamping ring 52 is fitted against the upper edge of the inner bag 5| and forces this portion of the bag against the metal ring 56 at a position above the annular member 6|. Binding wire is wrapped around the upper edge of the outer bag '50 and at a position opposite the retaining ring 62 so that both bags are rigidly secured to the depending ring 5S and thus held in spaced position. At a position approximately midway of the length of the outer bag there is a pair of circular tension springs E3 contacting the outer bag surface and secured thereto by being sewn within a canvas matrix 64 which also serves to position the springs apart. The purpose of these springs will be apparent when the function of the lter has been explained.

In order that the inner light bag 53 may be readily replaced, usually day by day since the crevices betweenthethreads of the bag tend to' ll with scum, a pair of hand operated adjustable clamps generally indicated c at 65 is employed, these clamps being placed diametricallyA opposite one another and so arranged as to detachably hold the lange'l' to the web 58. An enlarged detailed View of these clamps is shown in Figure AA thumb screw 66 is threaded through the web58, this -screw'being provided with a sleeve 61 which fits somewhat loosely in a rectangular plate member 68 which has a cutaway portion 69. The inner end of the plate 68 is adaptedrto press aga-inst the outer surfaceof the flange 51 when the thumb screw S5 is tightened so thatthe latter is forced against the web 58. -f If desired, any suitable type of vgasket 'l may be inserted between the flange 5l and the web 58 as seen in Figure l1. The'plate element 68 is provided at its outer end with a longitudinally extending opening 1|, this openingY projecting inwardly as far as the sleeve 61 and containing a compression spring l2 which is held in place by a plug 13'. The purpose of this spring is to force the sleeve 61 against the threaded shank of the thumb screw and thus to produce friction between the shank and the surrounding members, including theplate 6.8'. There is a stop member '14 projecting upwardly from the web 58 so as to be contacted by the plate 58 as the latter is caused to swing when the thumb screws turn. Assuming that the thumb screw of the clamp illustrated at the lower right hand corner of the compartment 30 (Figure 10) has been rotated clockwise, the plate 68 will also have been rotated clockwise due to the urge of the spring 'l2 until the lower inner edge ofthe plate has come into contact with the stop member 14. This is the position shown in Figure 10 and it would normally cause the plate member to be pointed die rectly toward the center of the bags 50, 5|. Further turningof the thumb screw when the plate has reached this position will no longer cause the plate to rotate, but instead will cause the plate to clamp tightly against the flange 5l' and thus hold the ring 5B rigidly in position. If it is desired to remove the double bag structure from out of the compartment, it is simply necessary to rotate the thumb screw counterclockwise and eventually the plate 53 will have rotated counterclockwise and assume the position shown by the dot-dash lines as indicated in the lower left hand corner of compartment 3lr(Figure 10). As stated hereinbefore, a pair of these clamping devices'are provided in compartment 3i) to clamp the flange 5l at diametrically opposite positions to the web 58. The compartment 30 is closed at the top by the plate 25 which is secured to the Walls thereof in any suitable manner as by screws T5.

The pipe 16 projects through an Opening in thev cover 25 so as to be in communication with the interior of the inner bag 5|. This pipe extends from the interior of the filter which is contained in compartment 3| and will be described presently. The main passageway through which the bags 5|), 5| are lled with fluid is comprised of an opening 'Il in the wall 28 and the opening communicates with the interior of the compart' ment 3|. Thus, the interior of the bag 5| is in communication with the exterior or discharge of the filter contained in compartment 3| through this opening.

vAssume that a iiuid consisting of a coolant and finely divided foreign material such as metal particles is introduced into the inner bag 5| through the opening Ti or the pipe 76, the fluid flows through the inner and outer bags 5|, 55

bythe action of gravity and any foreign particles in the liuid are either caught mainly by the inn-er bag l or' by the outer bag 5U, so that the coolant uponV reaching the pump 32 is in anv exceptionally clear state.

It is apparent that while the bags 50, 5l' are filled with fluid the hydrostatic pressure of the fluid will cause the periphery of the bags to press outwardly against the confining action of thesprings 63 and will stretch these springs. However, upon emptying the bags of fluid as when ilow through the opening l1 is stopped, the bags are caused to collapse to a shape indicated in Fig. 9 by the compression action of the springs. This radial movement of the bags inwardly and outwardly as determined by the emptying and filling of the bags with fluid tends to prevent any caking of the solids within the interstices between the webs or threads ofthe cloth or canvas. Any lumps of material are caused to break up when the springs compress the bags and the broken mass immediately drops to the bottom of the bags. Any material which may have collected on the outside of the outer bag is, at the same time, dropped to the bottom of the compartment. The bottom plate 26 of the compartment preferably has a tapered position with the inclination extending downwardly toward the wall 28 so that allvthe sludge particlesexuded by the bags or any broken masses of scum from the outside of the outer bag settle into the lowermost part of the compartment 3l) and be received by an opening '18 which extends through a heavy plate member 'i8' forming a portion of the bottom closure plate. The sludge or semiliquid mass passes through the opening 1B by gravity into a swarf pump indicated generally at 19 which will be described presently.

The filters 50, 5I in compartment 30 actually constitute the second stage of the ltering system of which the first stage is formed by a filter contained in compartment 3|. The first stage filters are quite similar to the second stage filters as described hereinbefore except that they extend in the upward direction which is opposite from the inverted filters of the second stage. It is apparent that in the second filter stage, the coolant is caused to pass through the bags due solely to gravity effects as the upper end of the inner bag is open to the atmosphere.

The manner in which the coolant is strained ofY its suspended foreign matter is illustrated in Figure l2. This View shows a fragment of one of the outer bags 84, 50 which is preferably made of coarse fabric material so as to leave a completely free opening a between each group of adjacent strands. The strands of the fabric are comprised of twisted threads or filaments in the usual manner and therefore have liber ends extending therefrom in all directions. Thus, extending inwardly of the opening a are a large number of bers or liber ends indicated at b. These fibers strain sediment from the iluid passing through the bag and, further, tend to collect the ne particles together and utilize the natural affinity between such microscopic particles for agglomerating them to a semi-solid mass as at c; These masses drop off as the bag expands and contracts due to pressure changes thereon, or are removed from' the system through the daily routine change of bags. As the bags are repeatedly cleansed and laundered, the sedimententrapping fibers become more numerous'so that the filtering action is enhanced.

Referring to Figure 4, the compartment which comprises the walls 23, 25, 28 and 26 is provided with an inwardly extending web 19 near the bottom and which carries an I -shaped ring 3Q.

The latter may be clamped to the web by a friction clamping device generally indicated at 8| similar to that which was described in connection withFigures 10 and l1. However, the thumb screw 5G is provided with an extremely long shank 82 which terminates near the top cover plate 25 in a knurled knob 83, the function of which is exactly the same as was eX- plained with respect to the thumb screw 66. A pair of clamping devices 8l at diametrically opposite positions may be employed as shown in Figure 10, together with suitable stops lll so that by rotating the knobs 63 counterclockwise (Figur-e l0) the L member 8d can be firmly secured to the web 79. On the other hand, by rotating the knob 83 counterclockwise this member is caused to be loosened from the web so that the filter can be removed from the compartment and inspected or replaced if necessary. The outer bag 84 and the inner bag 85 are similar to those which were described in connection with Figure 8 in which the bag 35 is made of light material in order to collect practically all of the scum obtained from the uid. This inner bag is also adapted to be removed daily. A pair of springs 63 are sewed in canvas shr-ouds about the outer bag and, also explained hereinbefore, serve to collapse the middle section of both bags when pressure is removed from the interior of the filter, thus avoiding any tendency for foreign material to cake on the outer surface of the outer bag.

It has been explained that the pipe 45 leading from the pump 33 terminates in a pipe i6 which is received by the inner bag B5. The fluid in flowing from the pipe d6 iills the interior of the bags Vand the space :bounded by the web 19' and the bottom closure member 2t with iiuid so that the fluid is nally forced out of both iilters into the space determined by the outer periphery of the outer bag Sil and the plates 23, 28, and 25.

As the level of the fluid becomes higher than the opening ll, the excess will flow into the compartment 3i) and ll the inner bag 5| of the second stage filter with fluid as was explained hereinbefore.

If for any reason, there is any stoppage of the fluid through the filters 84, 35, a back pressure will develop within the bag S5 and it is desirable under these circumstances to permit the iiuid within the bag to flow directly into the second stage bag 5l. For this purpose, a pipe 86 is provided which extends into the interior of the bag 85 and is in communication through pipes 3l, 8S and Sil with the pipe 'it which leads to the second stage filter. The pipe 39 can be made of a transparent plastic material so that by observing whether or not fluid is flowing therethrough into the second stage filter it can be determined as to any excess pressure in the first stage brought about by stoppage of the fluid through the filter bags Se, 85. If there is any considerable flow through the transparent pipe 89, the apparatus is shut down and the bags 85, 8!! inspected and if necessary replaced.

It is apparent that the provision of the pipe 88 and the openings S all serve to prevent any starving of the circulating pump in the event of partial stoppage 0f the flow through the filter units. This arrangement insures a positive and unfailing flow of coolant to the grinding wheel under any and all conditions and the inherent eiciency fromfalling below practical requirements. 1

As in the case of the compartment 30 the bottom closure member 26 of compartment 3| is given a downwardly extending slope toward the center of the apparatus so that any sludge or other semi-solid mass which drops -from the inner filter ba-g 85 will collect andwill ilow by gravity through a pipe 90 into the opening 18 which communicates with the sludge or swarf pump 19.

Swarf pump `The sludge or swarf pump 19 (Figure 3) is providedA for the purpose of expelling the sludge which had collected at the lowest or deepest part part of the two compartments 30, 3|. The details of the pump are shown for the most part in Figures ,5, 6 and 1.v The pump casing is indicated at and may have a rectangular or round shape, splitin' two parts at the middle. The parts are bolted together at the ears 92`and flat surfaces are provided at each side of the pump casing in the region of these ears so that the bolts l93 passing through the ears can also secure vthe pump to the heavy plate 18' forming part of the bottom Vclosure members 26. Within the casing 9| there isa pair of adjacently positioned, longitudinally extending openings S4, 95 separated :by a partition 0S. These openings are terminated by a plate 01 to which is secured a plunger 98. This `plunger may have an annular groove which contains a packing ring 99 and is adapted slidably to move along a circularbore |00 formed in an extension l0! of the casing.` The plate 01 is of circular configurationand is also adapted to slide within a' circular bore |02 formed within the casing Si. The openings 04, 95 loosely receive rods |03, |04 respectively which are secured at one end to the plate 91 and at the other end are counter-bored to receive a rod 05 of small diameter. There is a flanged plug |06 surrounding each rod 05 so that a completely enclosed space is provided between each rod |03, |04, the partition 06, the plate 91 and the iianged portion cf-the plug |05. Within each' of these spaces there is a compression spring |01 loosely surrounding the rods |03, |04, the purpose of which will ce explained presently. A conically shaped sealing member |08 abuts the plugs |06 and loosely ts the rods |05. At the extreme right hand end of each of the rods |05 a flanged sleeve |09 is carriedM within `the casing and slidably lits about the rods |05. This sleeve serves asa support for the rods as they reciprocate during operation `to eject the sludge material as will be described presently. The rods |05 are secured to the rods |03, |04by means of a pair of longitudinally extendingbolts l0, the head of which engages the right hand end of each rod |05 and the .threads at -the other end engage corresponding threads-in a counterbored opening within the rods i031, |00. It is apparent that the rods |03, |04 and the rods |05 constitute composite pis- .tons which are adapted to be moved to the left by the pressure yexerted at the springs |01 and also adapted to be moved to the right when pressure is exerted at the left hand end of the piston 98. VIt is evident ythat these pistons |05 opcrate in parallel since both of them are secured to the common retaining plate 91 through the rods |03, |04. Y 1

To the right of the'fiiced'sleeves |00 there is a thin washer which bears againsta so-called I star valve l I 2 held in place by a circular nut |13.

Vof each star valve |2.

'A'Washer or gasket H5 abuts the facing of the pump casing. The star valve ||2 is preferably madeof an expansible material such as rubber and is constituted of a series of radially extending slots or grooves, the arrangement being such that whena semi-fluid material is pressed against these slots, the latter are permitted to expand temporarily so as to allow the semi-solid material to pass through the valve into a pipe H5. This pipe is carried on a hub member ||1 which is bolted or screwed as indicated at |118 tothe valve casing 9|. It will be noted in Figure 6 that the plungers |05 are shown in a retracted position due to the absence of pressure in the chamber |00 and due also to the retraction force eX- erted by the springs |01.

Directly above the ends of the plungers |05 there are two openings |`|9 passing through the cylinder wall 0| and communicating with the opening 18 in the heavy plate member 30 forming part of the lower cover 20 of the chambers 30, 3|. The pipe IIS communicates through a conduit |20 with a pipe |2i 'whch leads to an upstanding compartment |22 provided with a turned over nozzle |25 (Figure 3). This nozzle serves as a discharge outlet for the sludge or other semi-solid material which has been ejected by the pistons |05 of the swarf pump through the conduits |20, |2| and |22. As the sludge collects in the upright pipe |22 a certain quantity of clear liquid may collect on top of the sludge and this liquid can nd its way back to compartment 3| through a screen |20 mounted on the wall 23. Y

In order to apply periodic pressure to the piston 98 and thus to give a reciprocative motion to the plunger |05, a pressure pipe |2| is threaded into the end of the casing extension |0|. This pipe is taken through the base 2 (Figure 2) to the main operating pump |25 which provides the necessary iluid pressure for the operatingy cylinder |26 of the reciprocating work bed 3 of the grinding machine. Consequently, as pressure is intermittently supplied to the cylinder |20 and its contained piston, a corresponding pressure is also applied to the piston 08 causing the plunger |05 to move to the right (Figure 5) and to force any sludge or other semi-solids which had collected in front of the plungers into the grooves From thence the semisolid material is forced into the pipe H0 and nally ejected from the machine at the nozzle |23 into any suitable receptacle (not shown). When pressure is relieved at the back of the piston 98 as when the table 3 is caused to move in a reverse direction and no fluid under pressure is contained within the pipe |2|,`the plungers |05 are caused to be retracted to the position shown in Figure 6 awaiting the next discharge of sludge to be dropped through the opening 10 (Figure 3).

From the foregoing, it is evident that there has been disclosed an improved form of filtering apparatus for Vremoving solids from lubricating fluids used in connection with metal cutting or metal abrading machines toyinsure that the lubricant is free from solid matter, even of microscopic size. While I have described my invention from the standpoint of employing two sets of filters connected in series and each set comprising a pair of lter bags, one of which is designel to be removed daily, it will be understood. that as many stages of filtering may be employed as is necessary to cleanse the lubricant and also as many bags within each lter set may also be imployed Ail" desired.` In addition to disclosing an improved -apparatus by which the solids are segregated from the lubricant liquid to a high degree of purity, there is also provision for automatically :removing the segregated sludge or semi-solid material from the machine so as to prevent any danger of its return into the lubricating system. If desired, the swarf pump could be manually controlled and manually operated to `provide any desired frequency of movement in case the pressure impulses obtained from the :main operating pump |25 are not sufficient to keep the passageway 'H' entirely clear of sludge.

It will be understood `that various modifications and arrangements in structure could be made without departing from `the spirit of my invention and, accordingly, I desire to comprehend such modifications and substitutions of equivalents as may be considered to come within the scope of the appended claims.

Having thus fully described my invention, what .l claim as new and desire to ,secure by Letters Patent, is:

l. In a filter; a first compartment having a iirst filtering unit opening downwardly therein, the open end of said unit being secured to the lower part of the wall of said compartment, a second compartment arranged to receive the overiiow from said rst compartment and having a second ltering unit opening upwardly therein, the open end of said second unit being secured to the wall of said second compartment beneath the point of entry of overiiow iiuid from said first compartment, an outlet port withdrawing filtered iiuid from said second compartment from around the filtering unit therein, means for supplying fluid to be filtered under pressure to the open side of said first unit, and liquid conducting means connecting the open sides of said uni-ts together and Awith said outlet whereby substantially constant rate of fluid iiow obtains regardless of the condition of the filtering medium therein,

`2. In a filter; a first compartment having a first filtering unit opening downwardly therein, the open end of said unit being secured to .the lower part of the wall of said compartment, a second compartment arranged to receive the over flow from said rst compartment and having `a second ltering unit opening upwardly therein, the open end of said second unit being secured to the wall of said second compartment beneath the point of entry of overflow fluid from said rst compartment, an outlet port withdrawing ltered fluid from said second compartment from around the filtering unit therein, means for supplying iiuid to be filtered under pressure to the open side of said first unit, and liquid conducting means connecting the open sides of said units together and with said outlet whereby substantially constant rate of fluid iiow obtains regardless of the condition of the filtering medium therein, the liquid conducting means connecting the filter inlets comprising a conduit passing betweenthe inlets and extending above the normal level of the fluid in the first compartment wherein a predetermined resistance to fluid flow through said first unit must be developed to make the liquid conducting effective;

3. In a filter; a iirst compartment having a rst iltering unit opening .downwardly therein, the eeen end of said unit being secured to the lower part of the wall of said compartment, a second of said second compartment beneath the point of entry of overflow ilud from said rst compartment, an outlet port withdrawing filtered uid from said second compartment from around the filtering unit therein, means for supplying fluid to be filtered under pressure to the open side of said rst unit, and liquid conducting means connecting the open sides of said units together and with said outlet whereby substantially constant rate of fluid iiow obtains regardless of the condition of the filtering medium therein, the liquid conducting means connecting the filter inlets comprising a conduit passing between the inlets and extending above the normal level of the iluid in the rst Vcompartrrient wherein a predetermined resistance to fluid flow through said rst unit must be developed to make the liquid conducting effective, and the 'liquid conducting means connecting the inlet of the second unit with said outlet comprising port ymeans in said second unit opening into said second compartment and above the normal level of the fluid in said second unit.

4. In a filter; a first compartment having a mounting ring therein adjacent the bottom, a first filter bag means mounted on said ring and extending upwardly, a second compartment adjacent said iirst compartment and arranged to receive the overow therefrom, a mounting ring in said second compartment beneath the point of entry of the overow fluid, a second filter bag 'means mounted on said ring and extending downwardly therefrom, a supply pipe opening into said first compartment to supply fluid to be liltered to the inside of said first bag means, an outlet opening from said second compartment to withdraw ltered iiuid therefrom from around said second bag means, a conduit passing from the inside of said first bag means to above said second bag means and extending above the normal level of iiuid in said first compartment whereby a predetermined resistance to flow through said rst bag means will cause bypassing of fluid therearound directly to the inlet of said second bag means, and a plurality of ports around the upper part of said second bag means beneath the mounting ring therefor and above the normal level of fluid therein whereby a predetermined resistance of fluid flow through said second bagmeans will bypass the fluid from the inlet thereof directly to said outlet.

5. An arrangement as claimed in claim l and in combination therewith, a sump for receiving contaminated iiuid to be filtered, and a pump operable to pump the fluid from said sump to the open side of said iirst liltering unit.

6. An arrangement as claimed in claim 1 and in combination therewith, afrst sump for receiving the iiuid to be ltered, a second sump for receiving filtered fluid from said outlet, and pumping means for conveying the filtered liuid away from said second sump and for conveying the uid from said liirst sump to the open side of said rst filtering unit.

'7. An arrangement as claimed in claim 1 lwherein each of the said filtering units comprises an inner filtering member and an outer filtering member spaced therefrom.

8. An arrangement as claimed in claim l wherein each of the said filtering units comprises an inner bag of finely woven fabric and an outer bag spaced from the inner bag and comprising a coarsely woven fabric.

OTTO MURRAY SUMMERS.

(References on following page) 1 3 REFERENCES CITED Ngmber The following references ane of record in the 19142584 file of this patent: UNITED .STATES PATENTS a 492,302 Number Nfame Date 1,044,074 Nugent Nov. 12, 1912 1,058,133 Yourtree Apr. a, 1913 Number 1,372,119 Congleton Manzz, 1921 8,675 1,456,919 Good May 29, 1923 ,o 2,168 1,663,322 Tekavec Mar. 30, 1928 '326,111 1,696,313 Liddell Dec. 25, 1928 Name Date Weinstein Jan. 9, `1934 Gieseler July 25, 1939 Reppmann Sept. 28, 1943 Summers Sept. 20, 1.949 FOREIGN PATENTS l Country Dato;l Great Britain of 1840 Great Britain of 1386 France of 1903 

